Piezoelectric crystal support



z m zm Apr-5E 9 35 H. POTTER PIEZOELECTRIC CRYSTAL SUPPORT Filed July 19. 1956 I INVENT OR HORACE/'3 POTTER ATTORNEY ire States Patent PIEZOELECTRIC CRYSTAL SUPPORT Horace R. Potter, Carlisle, Pa., assignor to Standard Electronics Corporation, Newark, N. .L, a corporation of Delaware Application July 19, 1956, Serial No. 598,821

9 Claims. (Cl. 310-9.1)

This invention relates to piezoelectric crystals and mounting means therefor and particularly to such crystals which are supported for operation by means of flexible members.

Piezoelectric crystals are in widespread use in many forms of electronic equipment and the physical arrangements for supporting crystals in the circuits in which they are used have been studied in great detail. As a result of this work many forms of supportsfor crystals have been devised to achieve the best performance from the crystal itself consistent with other considerations.

One form of support which has found wide acceptance is the arrangement consisting of two fine spring wires soldered directly to the metal plated surfaces of the crystal plate to physically support the crystal and also make electrical connection with the crystal electrodes. The two supporting wires thus form the lead wires to the crystal and since they are very fine and generally attached at a nodal point of the crystal plate the mechanical activity of the crystal is unimpaired.

Many different arrangements of flexible supports are known in the prior art which provide a mechanical system that permits the crystal to have the desirable electrical characteristics. In particular it is desirable that the support wires have a high degree of compliance to prevent the transmission of mechanical shock and this is generally accomplished by suitable bends in the spring wire support together with localized mass placement which can be in the form of balls of solder. Crystals supported in this fashion have a high Q and their electrical characteristics are substantially unimpaired by the mechanical supports.

An object of the present invention is to provide an improved support unit for piezoelectric crystals.

A further object is to provide an improved resiliently supported crystal unit with limit stops.

A further object is to provide limit stops for the spring support members of a crystal to control the maximum excursion of the mechanical system.

Still another object is to provide a crystal mount that protects the crystal from mechanical shocks.

Mechanical limit stops for piezoelectric crystals are known but have not come into widespread use due, in part, to the disadvantages of heretofore known arrangements. In accordance with the present invention limit stops are provided in predetermined spaced relation to the spring wire supports of a piezoelectric crystal to permit unrestricted operation of the crystal plate for normal mechanical excursions but limiting the deflection of the support wires therefor at a definite point. This arrangement does not apply the contact with the limit stop to the crystal plate itself but rather acts upon the support therefor and in effect produces a much stiifer support system for deflection forces in excess of a predetermined amount.

For a more complete understanding of the present invention reference is made to the following detailed description of a particular embodiment of the invention as 2,830,203 Patented Apr. 8, 1958 applied to a particular resiliently supported crystal. The description and the accompanying drawing are to be considered as illustrative of the principle of the invention which can readily be applied to other embodiments without departing from the scope of the invention.

In the drawings:

Fig. 1 is a plan view of a resiliently supported crystal unit embodying the invention;

Fig. 2 is a side elevation view of the unit of Fig. 1;

Fig. 3 is an end elevation view of the unit of Fig. 1; and.

Fig. 4 is a side elevation view of a modification.

Referring now to Figs. 1, 2 and 3, a plug-in crystal unit is shown comprising a base 11 having a peripheral groove 12 into which a cover unit, not shown, is sealed to form a hermetically sealed inclosure for the crystal unit. The base 11 has two insulator inserts 13 through which project prongs 14 the exterior portions of which are adapted to plug into a suitable socket and the interior ends 15 and 16 serving as electrical terminals and mechanical support points as will hereafter appear.

A pair of fine spring wires 17 and 18 are soldered to the respective terminals 15 and 16 and after suitable bends to obtain the desired compliance stand as vertical parallel supports, best seen in Fig. 3. Between these supports 17 and 18 a crystal plate 19 is positioned supported on two lead wires 21 and 22. The lead wires 21 and 22 are soldered directly to the metal plating on the major surfaces of crystal 19 at 20 and are connected to the respective supports 1'7 and 18 by solder balls 23. The arrangement of the support wires 17 and 18, the lead wires 21 and 22 and the solder balls 23 are chosen for the desired operating characteristics.

The limit stop for the support wires 17 and 18 is provided in the described embodiment by relatively stiff wires 25 and 26 which may be of suitable spring material such as Phosphor bronze and may be relatively stiff compared to the support wires 17 and 18. Generally the limit stop wires 25 and 26 will be of greater cross sectional diameter than the support wires 17 and 18. The limit stop wires 25 and 26 are soldered to the respective terminals 15 and 16 and extend upwardly therefrom toward a central position where they terminate in substantially horizontal closed loops 27 and 28 which inclose the respective support wires 17 and 18. The wires 17 and 18 will in general be centered within the loops 27 and 28 with enough clearance to permit normal activity of the crystal unit and the support wires 17 and 18. For limiting undue excursions of the support wires 17 and 18, the loops 27 and 28 limit the motion of the wire supports 17 and 18 upon contact with the loops 27 and 28 and while in contact form a more rigid, yet still flexible, support system with respect to further deflection forces. If desired, of course, the limit stop loops 27 and 28 can be supported to form effectively rigid stops.

The modification of Fig. 4 differs from the embodiment of the preceding figures primarily in mounting the crystal plate 19 so that all portions thereof are above the uppermost portions of the limit stop loops 27 and 28. With this arrangement there is no possibility of the crystal 19 itself coming into contact with the members 25 and 26 and thus impairing its operation. In general the arrangement and proportioning of the various elements can be such that the desired limiting action can be imposed upon the desired support member without any danger of imposing mechanical limit contact with the crystal itself.

Throughout this specification and claims the terms crystal and piezoelectric crystal are to be interpreted in their broad sense and not limited to quartz crystals which is only one of the materials exhibiting that property.

Many modifications will now be apparent to those skilled in the art in the light of the present teaching and the invention therefor is considered to include such modifications within the scope of the appended claims.

I claim:

1. A piezoelectric unit having a pair of terminals and comprising a piezoelectric crystal element, metallic coatings formed integral with the major faces or". said crystal element, crystal supporting conductive lead wires soldered to said crystal coatings substantially at the centers of said major faces, conductive bent spring wire mounts carrying said lead wires and joined thereto by a solder mass the other ends of said spring wires being secured to said terminals, and a pair of limit stops formed of relatively stifl? wires secured at one end to said terminals and extending generally toward said solder mass, the free end of said stilt wires being formed into loops encircling said spring wire mounts respectively near said solder mass, the normal position of said mounts providing apredetermined clearance from said loops.

2. A unit in accordance with claim 1 in which the lower edge of said crystal element is approximately parallel with the plane of said loops and said edge is above the plane of said loops.

3. A piezoelectric unit comprising a pair of terminals, a piezoelectric crystal element, conductive bent spring Wires supporting said crystal and electrically connecting said crystal to said terminals, and a pair of relatively stifl wires fixed to said terminals and extending toward the end of said spring wires adjacent said crystal, the free ends of said stilt Wires being formed into loops encircling said spring wires with predetermined clearance.

4. A unit in accordance with claim 3 in which said crystal is positioned wholly above the plane of said loops.

5. In a piezoelectric unit having a piezoelectric crystal supported solely by a pair of compliant spring wires connected thereto, means for limiting the deflection of said spring wires in the neighborhood of their connection to said crystal comprising substantially rigid mechanical stops spaced a predetermined distance from said spring wires.

6. In a piezoelectric unit having a piezoelectric crystal supported by a pair of compliant spring wires connected thereto, means for limiting the deflection of said spring wires in the neighborhood of their connection to said crystal comprising substantially rigid mechanical stops spaced a predetermined distance from said spring wires.

7. A piezoelectric unit comprising a pair of fixed supports, a piezoelectric crystal element, a pair of relatively long flexible spring wires secured to said fixed supports at one end and supporting said crystal at the other ends thereof and relatively rigid members secured to said supports and extending toward said other ends and surrounding said spring wires at said other end with a predetermined clearance therebetween.

8. A piezoelectric unit comprising a pair of fixed supports, a piezoelectric crystal element, flexible spring wire means secured to said fixed supports at one end and supporting said crystal at the other end thereof, and relatively rigid stop means secured to said unit and extending toward said other end with predetermined spacing from said spring wire means adjacent said other end for limiting any direction of deflection of said spring wire means.

9. In a piezoelectric unit having a piezoelectric crystal supported by a pair of compliant spring wires connected thereto, means for limiting the deflection of said spring wires in the neighborhood of their connection to said crystal comprising a substantially rigid mechanical stop spaced a predetermined distance from at least one of said spring wires.

References Cited in the file of this patent UNITED STATES PATENTS 1,949,149 Ellis Feb. 27, 1934 2,275,122 Ziegler Mar. 3, 1942 2,416,067 Robb Feb. 18, 1947 2,441,139 Fair May 11, 1948 FOREIGN PATENTS 578,290 Great Britain June 21, 1946 

